Wow...now that this thread is more than two years old, I'm happy to report there have been no more falls. I had one other fall a few weeks after this originally posted but it was due to a flat tire. I probably wouldn't have fallen if I wasn't clipped in, but at least it wasn't because of inattentiveness.

Also, I switched over to SPD 520 pedals about a year ago and like them much better than the Speedplays.